Dry Shot and LTFT
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Teching In
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Dry Shot and LTFT I posted last week about issues I have with a C6 A6...in summary with stock air filter and descreened MAF my LTFT's are around 8 or so....with Blackwing and descreened MAF they're around 20...I am using a 100 dry shot and can easily make both setups run about an 11 A/F ratio on wideband.
Ultimately I'm going to get a tune and "fix" the LTFT's but for now which set up would be best for overall performance both NA and dry shot? With the higher LTFT's is the Blackwing helping performance at all?
Thanks in advance
Ultimately I'm going to get a tune and "fix" the LTFT's but for now which set up would be best for overall performance both NA and dry shot? With the higher LTFT's is the Blackwing helping performance at all?
Thanks in advance
Sure the Blackwing is helping. It's all about Volumetric Efficancy. Anytime you help airflow VE goes up, this means through out power band. You'll make more power quicker this way.
The ltft are just compensating for this new free flowing system. I don't think you'll really see/feel much diff running with or with out the BW, however, you may see it in a 1/4 run or on the dyno. Either way you will not hurt anything.
11.0:1 a/f is a little rich for a 100 shot, but certainly won't hurt anything. You can rotate your nozzle(s) slightly to allow some of the hit to bypass the MAF wire and thus reduce inj duty cycle for a leaner wot a/f. Sometimes even aiming one nozzle back into the air stream will give desired a/f. keep an eye on things as the ltft can take a couple hundred miles to readjust (or at least partially) on it's own and this will slowly change a/f. A base tune as you know is what is needed, then nozzle tuning and maybe a slight tweek with the PE Multiplier for desired final a/f.
Did your codes go away?
Robert
The ltft are just compensating for this new free flowing system. I don't think you'll really see/feel much diff running with or with out the BW, however, you may see it in a 1/4 run or on the dyno. Either way you will not hurt anything.
11.0:1 a/f is a little rich for a 100 shot, but certainly won't hurt anything. You can rotate your nozzle(s) slightly to allow some of the hit to bypass the MAF wire and thus reduce inj duty cycle for a leaner wot a/f. Sometimes even aiming one nozzle back into the air stream will give desired a/f. keep an eye on things as the ltft can take a couple hundred miles to readjust (or at least partially) on it's own and this will slowly change a/f. A base tune as you know is what is needed, then nozzle tuning and maybe a slight tweek with the PE Multiplier for desired final a/f.
Did your codes go away?
Robert
two different things. Fuel trims cut off at WOT so they aren't an issue when you shoot n2o. Now, for tuning the fuel trim and maf, this is a pretty good write up. Don't know if it is all the same for C6s though.
I think your Ok also.
I am comparing my current tune to the factory tune, I am running a Blackwing (C-5) and descreened MAF and the difference is about 6.7 % increased VE over stock, and my MAF table has increased 15% in some areas.
Last log LTFT -5% so I still have some tuning to do (Reflects the first run with headers).
Getting your VE table and MAF Table in order will bring those LTFT in line.
I am comparing my current tune to the factory tune, I am running a Blackwing (C-5) and descreened MAF and the difference is about 6.7 % increased VE over stock, and my MAF table has increased 15% in some areas.
Last log LTFT -5% so I still have some tuning to do (Reflects the first run with headers).
Getting your VE table and MAF Table in order will bring those LTFT in line.
Last edited by Beer99C5; Mar 11, 2007 at 07:40 PM.
Originally Posted by Todd157k
two different things. Fuel trims cut off at WOT so they aren't an issue when you shoot n2o. Now, for tuning the fuel trim and maf, this is a pretty good write up. Don't know if it is all the same for C6s though.
If your LTFT's are negative (pulling fuel for a percieved rich condition) they are dropped at WOT to make sure, again, that you aren't lean at WOT. This is why when doing a base tune we try to get all LTFTs into the 0 to -5 area, so not to affect the WOT a/f.
One more thing to add, the LTFT can vary day to day like 10%, but that's what they should do concerning changes in Barametric Pressure, Ambient air temp and so on. These are some smart cars.
Robert
Originally Posted by Todd157k
two different things. Fuel trims cut off at WOT so they aren't an issue when you shoot n2o. ....
Not really so... if they are positive near entry of PE they can lock and carry over through WOT. If they are higher down low... say 2500 they lock in at 8-12% and you mistakenly base your WOT tune on that, then the tune is based on a trim adding 8-12%!! This is bad. Upwards of 4500 say, they may be lower; like in the 4-8% range. Now when you go WOT you need 4-8% more fuel than you are giving it to keep it at the AFR that you arrived at earlier tuning based on a pull from down low.
Positive fuel trims are a no-no for consistent fueling.
